A vane-type valve timing control apparatus is known, which controls opening-and-closing timing of an intake valve or an exhaust valve by changing a rotation phase between a driving shaft and a driven shaft of an internal combustion engine. The vane-type valve timing control apparatus is equipped with a housing integrally rotating with the driving shaft and a vane rotor integrally fixed to the driven shaft inside the housing, and relatively rotates the vane rotor by supplying operation oil to a pressure chamber defined in the housing, such that the opening-and-closing timing is controlled.
Generally, in this kind of valve timing control apparatus, a cylindrical shoe housing which accommodates the vane rotor is supported between a front plate and a rear plate in an axial direction. A tightening bolt penetrates a through hole defined in a shoe part of the shoe housing from the front plate side, and is tightened to a female thread hole defined in the rear plate. JP 2009-215881A (WO 2008/004362 A1) describes a flat (countersunk) head bolt as the tightening bolt.
The flat head bolt can reduce an axial length of the bolt which includes a bolt head, compared with a pan head bolt or a cap bolt. In case of the pan head bolt or the cap bolt, the tightening axial tension is applied in parallel. The seat surface of the flat head bolt and the seat surface of the front plate have taper shape with cone angle of about 90 degrees. So, in case of the flat head bolt, the tightening axial tension spreads outward in the radial direction which is the direction of the normal to the seat surface. Therefore, depending on the size and the position of the shoe part of the shoe housing, a part or all of the range to which the tightening axial tension is applied may become outside of the shoe part. In this case, the tightening axial tension is not effectively transmitted to the shoe part, and there is a possibility that the shoe housing has a looseness and a position deviation in the rotational direction due to the impulse force and vibration accompanying the operation of the vane rotor.
If the tightening torque is simply increased too much to be larger than a proper torque, the flat head bolt may have fracture.